In recent years, due to the advantages of high efficiency, high power factor and high torque density, permanent magnet motors have been attracting increasing interest in commercial electric vehicles.
The patent literature “Rotating Motor” with the publication number CN101741154A is proposed that compared with the surface mounted and the surface embedded structure, the embedded permanent magnet motor can utilize the reluctance torque to improve the torque performance and speed range. Meanwhile, the full utilization of the reluctance torque can effectively control the back EMF amplitude of the permanent magnet motor in the electric vehicle, which is beneficial to the operation of the motor under the fault condition. However, the output torque of the permanent magnet motor is composed of permanent magnet torque and reluctance torque, and they are output at the same time, so the permanent magnet torque and reluctance torque cannot be controlled independently.
The patent literature “Method for improving torque density of motor and radial and axial flux parallel permanent magnet motor” with the publication number CN104716754A is put forward which improves the torque density by combining radial and axial flux and putting surface mount permanent magnet on the radial and axial direction of rotor simultaneously. However, this scheme does not separate the radial and axial magnetic field and does not take into account the reluctance torque of the motor, so it cannot be used in wide speed range.